The human high temperature requirement A (HTRA) family of serine proteases are ubiquitously expressed PDZ-proteases that are involved in maintaining protein homeostasis in extracellular compartments by combining the dual functions of a protease and a chaperone. HTRA housekeeping proteases are implicated in organization of the extracellular matrix, cell proliferation and ageing. Modulation of HTRA activity is connected with severe diseases, including Duchenne muscular dystrophy (Bakay et al. 2002, Neuromuscul. Disord. 12: 125-141), arthritis, such as osteoarthritis (Grau et al. 2006, JBC 281: 6124-6129); cancer, familial ischemic cerebral small-vessel disease and age-related macular degeneration, as well as Parkinson's disease and Alzheimer's disease. The human HTRA1 contains an insulin-like growth factor (IGF) binding domain. It has been proposed to regulate IGF availability and cell growth (Zumbrunn and Trueb, 1996, FEES Letters 398:189-192) and to exhibit tumor suppressor properties. HTRA1 expression is down-regulated in metastatic melanoma, and may thus indicate the degree of melanoma progression. Overexpression of HTRA1 in a metastatic melanoma cell line reduced proliferation and invasion in vitro, and reduced tumor growth in a xenograft mouse model (Baldi et al., 2002, Oncogene 21:6684-6688). HTRA1 expression is also down-regulated in ovarian cancer. In ovarian cancer cell lines, HTRA1 overexpression induces cell death, while antisense HTRA1 expression promoted anchorage-independent growth (Chien et al., 2004, Oncogene 23:1636-1644).
In addition to its effect on the IGF pathway, HTRA1 also inhibits signaling by the TGFβ family of growth factors (Oka et al., 2004, Development 131:1041-1053). HTRA1 can cleave amyloid precursor protein (APP), and HTRA1 inhibitors cause the accumulation of Aβ peptide in cultured cells. Thus, HTRA1 is also implicated in Alzheimer's disease (Grau et al., 2005, Proc. Nat. Acad. Sci. USA. 102:6021-6026).
On the other hand HTRA1 upregulation has been observed and seems to be associated to Duchenne muscular dystrophy (Bakay et al. 2002, Neuromuscul. Disord. 12: 125-141) and osteoarthritis (Grau et al. 2006, JBC 281: 6124-6129) and AMD (Fritsche, et al. Nat Gen 2013 45(4):433-9.)
A single nucleotide polymorphism (SNP) in the HTRA1 promoter region (rs11200638) is associated with a 10 fold increased the risk of developing age-related macular degeneration (AMD). Moreover the HTRA1 SNPs are in linkage disequilibrium with the ARMS2 SNP (rs10490924) associated with increased risk of developing age-related macular degeneration (AMD). The risk allele is associated with 2-3 fold increased HTRA1 mRNA and protein expression, and HTRA1 is present in drusen in patients with AMD (Dewan et al., 2006, Science 314:989-992; Yang et al., 2006, Science 314:992-993). Different animal models have confirmed that over-expression of HtrA1 Induces AMD-like phenotype in mice. The hHTRA transgenic mouse (Veierkottn, PlosOne 2011) reveals degradation of the elastic lamina of Bruch's membrane, determines choroidal vascular abnormalities (Jones, PNAS 2011) and increases the Polypoidal choroidal vasculopathy (PCV) lesions (Kumar, IOVS 2014). Additionally it has been reported Bruch's membrane damage in hHTRA1 Tg mice, which determines upon exposure to cigarette smoke 3 fold increases CNV (Nakayama, IOVS 2014)
Age-related macular degeneration (AMD) is the leading cause of irreversible loss of vision in people over the age of 65. With onset of AMD there is gradual loss of the light sensitive photoreceptor cells in the back of the eye, the underlying pigment epithelial cells that support them metabolically, and the sharp central vision they provide. Age is the major risk factor for the onset of AMD: the likelihood of developing AMD triples after age 55. Smoking, light iris color, gender (women are at greater risk), obesity, and repeated exposure to UV radiation also increase the risk of AMD. There are two forms of AMD: dry AMD and wet AMD. In dry AMD, drusen appear in the macula of the eye, the cells in the macula die, and vision becomes blurry. Dry AMD can progress in three stages: 1) early, 2) intermediate, and 3) advanced dry AMD. Dry AMD can also progress into wet AMD during any of these stages. Wet AMD (also known as exudative AMD), is associated with pathologic posterior segment neovascularization. The posterior segment neovascularization (PSNV) found in exudative AMD is characterized as pathologic choroidal neovascularization. Leakage from abnormal blood vessels forming in this process damages the macula and impairs vision, eventually leading to blindness. Treatment strategies for wet AMD are few and palliative at best. There is therefore an unmet medical need in the provision of effective drugs to treat macular degenerative conditions such as wet and dry AMD. WO 2008/013893 claims a composition for treating a subject suffering from age related macular degeneration comprising a nucleic acid molecules comprising an antisense sequence that hybridizes to HTRA1 gene or mRNA: No antisense molecules are disclosed. WO2009/006460 provides siRNAs targeting HTRA1 and their use in treating AMD.